Biomedical subjects

I H Young

Publications and source records attributed to I H Young.

29 records · Page 2Linked to original sources

PubMed1989

Effect of low dose nebulised morphine on exercise endurance in patients with chronic lung disease.

Low dose nebulised morphine may relieve dyspnoea through a direct effect on lung afferent nerves. To study this further 11 adult patients with advanced chronic lung disease (FEV1 range 0.4-1.41), whose exercise endurance was limited by dyspnoea, were entered into a double blind, randomised, crossover study in which low dose morphine or a placebo was inhaled. The effects were assessed by an endurance exercise test at 80% of maximum work load. One hour after a control endurance test patients inhaled 5 ml of morphine 1 mg/ml or isotonic saline for 12 minutes from a jet nebuliser. An endurance exercise test was repeated 15 minutes later and change in endurance time recorded. The two endurance tests were repeated on a separate day, before and after inhalation of the alternative solution. In all tests 100% oxygen was inhaled from a demand valve. The mean (SD) increase in endurance time was significantly greater after the subjects had inhaled morphine (64.6 (115) s, 35%) than after placebo (8.9 (55) s, 0.8%; p less than 0.01). The mean dose of morphine nebulised was 1.7 (0.66) mg, giving a mean inhaled dose of about 0.6 mg, on the assumption of 30% retention of the nebulised dose by each patient. No side effects were reported. Possibly small amounts of morphine delivered to the lungs act directly on lung afferent nerves to reduce dyspnoea.

Administration, Inhalation↗

PubMed1989

The oxygen delivery characteristics of the Hudson Oxy-one face mask.

The inspired oxygen fraction (FIO2) delivered by the Hudson Oxy-one face mask was measured under changing conditions of ventilation, oxygen flow rate to mask, and mask fit. A single trained subject sat in a body plethysmograph to measure ventilation and breathed at a constant rate of 15 per minute at three different tidal volumes, of approximately 0.3, 0.6, and 1.2 litres, from the mouthpiece in the plethysmograph. The Oxy-one face mask was fitted to a plaster-of-Paris face model on the outside of the plethysmograph in a loose and then in a tight fashion. Oxygen concentration was continuously monitored from a point in the metal tube connecting the face model to the mouthpiece. The tightly fitting mask demonstrated an orderly reduction in FIO2 as ventilation increased and oxygen flow rate to the mask decreased. The mean FIO2 at a ventilation of 4.5 l.min-1 and 8 l.min-1 oxygen flow was 78% and this fell to 27% at a ventilation of 16 l.min-1 and oxygen flow of 2 l.min-1. The loosely fitting mask demonstrated larger SD of measurements and lower mean maximum FIO2 values of 46 to 49% and these fell in an irregular fashion to similar minimum values as ventilation increased and oxygen flow decreased. Although the precise definition of the FIO2 for each breath from the changing concentration during each inspiration was not possible, these results indicate that FIO2 changes in a predictable way as a function of ventilation and oxygen flow, if the mask is close fitting. This method could be conveniently used to study other oxygen delivery systems.

Evaluation Studies as Topic↗

PubMed1987

The distribution of ventilation-perfusion ratios in the lungs of newborn foals.

The distributions of ventilation-perfusion ratios, and the effects of 100% oxygen administration on the distributions, were studied in 3 foals from 4h to 9 days of age, using the multiple inert gas elimination technique. The distributions were calculated from the pulmonary clearance of 6 inert gases following infusion into a peripheral vein of a solution containing the inert gases. The results from a total of 8 studies showed several consistent features. The major findings were (i) the absence of low ventilation-perfusion ratios, i.e. regions where blood flow was greatly in excess of ventilation; (ii) the presence of variable right to left shunt; (iii) a reduction in this shunt with increasing post-natal age; (iv) the presence of a separate high mode of ventilation-perfusion ratios where ventilation was greatly in excess of blood flow and; (v) the observation that breathing enriched oxygen mixtures for 40 min did not increase the right to left shunt in any foal at any age studied. These studies indicate that hypoxaemia in the neonatal foal is attributable to right to left shunt which may be intrapulmonary or intracardiac, or both, rather than overperfusion of poorly ventilated lungs.

Age Factors↗

PubMed1985

Ventilation-perfusion relationships in symptomatic asthma. Response to oxygen and clemastine.

Continuous distributions of ventilation-perfusion (VA/Q) ratios were measured in ten subjects with moderately severe symptomatic asthma. Six of the subjects had only minimal VA/Q inequality (mean log SD of bloodflow 0.5) despite having airways obstruction similar to that in the four subjects with marked VA/Q inequality (mean log SD of bloodflow 1.0). The six patients with minimal VA/Q inequality developed marked widening of their VA/Q distributions while breathing 100 percent oxygen (mean log SD bloodflow 1.1), and four of these patients maintained more modest widening after receiving an intravenous antihistamine, clemastine (mean log SD bloodflow 0.75). The four subjects with a wide control VA/Q distribution showed smaller changes while breathing pure oxygen and no change after receiving clemastine. FEV1 improved with clemastine treatment in the first four patients only. The results suggest that the majority of patients with moderately severe asthma have compensatory pulmonary vasoconstriction, causing better VA/Q matching which is responsive to hypoxia and, possibly, histamine. The data demonstrate a relationship between active compensatory vasoconstriction and airway sensitivity to antihistamine.

Adult↗

PubMed1985

Use of protected telescoping brush system in the management of bacterial pulmonary infection in intubated patients.

The diagnosis of pulmonary infection remains a major problem in the management of intubated patients with respiratory failure. We performed fibreoptic bronchoscopy and protected telescoping catheter brushing in 25 such patients, in order to assess the role of this technique in the diagnosis of bacterial pulmonary infection. All patients were intubated, demonstrated lung field opacities on chest radiograph and 23 had bacteria grown from tracheal aspirate culture. A single microorganism was recovered from plugged telescoping catheter (PTC) brush in eight patients, two or more organisms in nine patients and eight had a sterile culture. These results led to a specific management decision in 13 patients. All patients were ventilated with positive pressure and a pneumothorax, attributable to the procedure, developed in two. The difficulties in assessing the sensitivity and specificity of this technique in human studies are outlined. This procedure appears to have a useful role in the diagnosis of pneumonia in these patients and in further evaluating the importance of bacterial colonization of the airways and its relationship to parenchymal lung infection.

Adolescent↗

PubMed1982

Pattern and time course of ventilation-perfusion inequality in exercise-induced asthma.

The relation between exercise-induced airway obstruction and changes in the gas exchange function of the lung was studied in 6 subjects with asthma. Continuous distributions of ventilation perfusion (VA/Q) ratios and spirometry were measured before and at intervals after an exercise challenge that caused a greater than 20% decrease in FEV1 or in peak expiratory flow rate (PEFR). Before exercise, all subjects had unimodal VA/Q distributions that were broader than normal (mean log SD of blood flow, 0.54) and all developed wider distributions 15 to 28 min after the start of the 8-min exercise challenge (mean log SD of blood flow, 1.02). Two subjects developed bimodal VA/Q distributions, but all distributions returned to baseline configuration within 58 min, usually before FEV1 and PEFR had returned to baseline values. There was no relation between the decrease in FEV1 or PEFR and the degree of VA/Q inequality. Aerosolized salbutamol resulted in improved spirometry and further narrowing of the VA/Q distributions in 3 subjects tested.

Asthma↗

PubMed1982

Bicycle endurance performance of patients with interstitial lung disease breathing air and oxygen.

The effect of supplemental oxygen breathing on bicycle exercise performance was studied in 16 patients in the assessment of their extent of impairment with interstitial lung disease (ILD). The mean maximal working capacity (W-Max) +/- 1 SD with incremental exercise breathing air was 107 +/- 43 W (60% predicted). There was no significant increase in W-Max with oxygen breathing (p less than 0.10, n = 12). On a separate day each patient performed 2 endurance studies at a constant submaximal work load (80% W-Max) inspiring air and 60% oxygen. The mean fall in arterial oxyhemoglobin saturation (SaO2%) during exercise in air was 8% (range, 1 to 23%). There was a significant improvement in exercise time (p less than 0.001) when patients exercised with oxygen. This increase in endurance was significantly correlated with the fall in SaO2% during the air study. The improvement in exercise time with oxygen was greatest in those with the most marked lung restriction. Blood lactic acid was reduced with oxygen breathing.

Air↗

PubMed1979

Effect of intrapulmonary hematocrit maldistribution on O2, CO2, and inert gas exchange.

The potential effect of intrapulmonary variations in hematocrit on gas exchange has been studied in theoretical models of the lung containing maldistribution of both hematocrit (Hct) and ventilation-perfusion (VA/Q) ratio. Hematocrit inequality enhanced gas exchange when units of low VA/Q were given a low Hct, arterial PO2 rising by as much as 14 Torr and PCO2 falling by up to 2 Torr depending on the particular distributions of Hct and VA/Q, whereas gas exchange was depressed when units of low VA/Q had a high Hct. After measuring inert gas solubilities in both dog and human blood of different Hct, the effect of Hct inequality on inert gas exchange was similarly assessed. Solubility was found to increase with HCT for less soluble gases. Because of this, conditions for enhancement of inert and O2 exchange by HCt inequality coincided, and it was found that in general the effects on O2 and inert gas transfer were quantitatively internally consistent. Even when Hct inequality was extreme, the resulting perturbation of inert gas concentrations was sufficiently small that the main features of the recovered VA/Q distributions were unaltered.

Animals↗

PubMed1979

Solubility of inert gases in homogenates of canine lung tissue.

The solubility of sulfur hexafluoride (SF6), ethane, cyclopropane, halothane, diethyl ether, and acetone in homogenates of dog lung tissue were measured and compared with values obtained in dog blood. The measurements were made to provide data for a method for determining distribution of ventilation, blood flow, and tissue volume (Physiologist 20: 95, 1977) and for reasons discussed, the blood was not washed from the tissue prior to homogenization. All gases except SF6 were significantly more soluble in blood than lung tissue, whereas SF6 was 3.7 times more soluble in tissue than blood. It was further found that SF6 is 5 times more soluble, and ethane is twice as soluble in tissue obtained from lungs containing blood than in tissue obtained from rinsed lungs, suggesting that measurements of parenchymal solubility made on tissue from sinsed lungs may be considerably in error for some lipid-soluble gases.

Animals↗

PubMed1979

Arterial blood gas tension changes at the start of exercise in chronic obstructive pulmonary disease.

In a previously reported study of a group of normal subjects, large decreases in arterial O2 tension (PaO2) of as much as 37 mm Hg were measured during the first 90 sec of slow stair-climbing exercise (chosen as a common daily exertion). This study reports the changes in PaO2, arterial CO2 tension (PaCO2), and ventilation in 7 patients with chronic obstructive pulmonary disease and resting hypoxemia during the first 90 sec of similar exercise. The patient group showed significantly smaller unsteady-state decreases in PaO2 starting from a smaller resting value (patient group, 72 +/- 2.6 mm Hg, mean +/- SE; normal group, 92 +/- mm Hg; P less than 0.001) and decreasing to a similar smallest value (patient group, 58 +/- 3.8 mm Hg; normal group, 65 +/- 3.4 Hg; P greater than 0.05). PaCO2 tended to oscillate around the resting value in both the patient group and the normal group, and the rates of increase in ventilation in the 2 groups were similar. The physiologic processes that could limit the unsteady-state decrease in PaCO2 in the patient group are analyzed, the analysis suggesting that a slower rate of increase in tissue consumption of O2 is most likely to account for the smaller decrease in PaO2.

Adult↗

PubMed1978

Changes in arterial blood gas tensions during unsteady-state exercise.

Arterial oxygen (Pao2) and carbon dioxide (Paco2) tensions and inspired minute ventilation were measured during the first 2 min of stair-climbing exercise in nine normal subjects. The subjects climbed a staircase at a rate of approximately 9 m vertical height every minute and arterial blood was drawn from an indwelling cannula at 15-s intervals. Large falls in Pao2 from a resting value of 92 +/- 2.0 (mean +/- SE) Torr to a lowest value of 65 +/- 3.4 Torr were recorded in the first 50 s of exercise while Paco2 oscillated around the resting value. Most subjects demonstrated an initial plateau of Pao2 for at least 7 s followed by a rapid fall and subsequent rise toward the resting level after 1 min. The falls in Pao2 measured were larger than those reported for laboratory exercise. The possible reasons for this discrepancy are discussed.

Adult↗